Comment 54 for bug 192629

You must add uid=1000 and gid=1000 to resolve this problem.

Change the FSTAB file like shown below.

/dev/sdb1 /media/SONGS vfat defaults,users,umask=000,uid=1000,gid=1000 0 1
/dev/sdb5 /media/BACKUP vfat defaults,users,umask=000,uid=1000,gid=1000 0 1
/dev/sdb3 /media/FILES40NEW vfat defaults,users,umask=000,uid=1000,gid=1000 0 1

Save the file and restart the computer. Create a folder called .Trash-1000 in the root of these partitions. Now, when you delete a file from these VFAT partitions, the files will move to Trash directly.

reference
http://ubuntuissues.wordpress.com/2008/06/19/cannot-move-files-to-trash/